Use APKPure App
Get 무음 카메라로 old version APK for Android
It will change the default camera app to silence the shutter tyeoeum.
Download existing version
https://drive.google.com/file/d/18D_1C2WNZrTXEyf75-6_cHkAU_vo9LKg/view?usp=drivesdk
If you want to use the existing version, do not perform automatic updates.
*Never use the app for illegal purposes